half of menstruating women have cramp-like pain
during their periods. The medical term for menstrual
pain is dysmenorrhea. Cramps are usually felt in the
pelvic area and lower abdomen, but can radiate to
the lower back or down the legs.
"Many girls have cramps severe enough to keep them
home from school," Rarick says. In fact, according
to Danforth's Obstetrics and Gynecology,
dysmenorrhea is the most frequent cause of
absenteeism from school among younger women. Rarick
says women seem to go through phases when cramps are
severe, then get better for several years, and then
maybe worsen again. She adds that most women find
they have less menstrual pain after having children.
Mechanically, cramps are like labor pains. Just as
the uterus contracts to open up the cervix (neck of
the uterus) and push out a baby, it contracts to
expel menstrual blood.
Often, after several years of menstruating or after
childbirth, the cervical opening enlarges. The
uterus doesn't have to contract as much to discharge
the menstrual flow, so there is less cramping.
Menstrual pain may also come from the bleeding
process itself. When the uterine lining separates
from the wall, it releases chemicals called
prostaglandins. Prostaglandins cause blood vessels
to narrow, impeding the supply of oxygen to the
uterus. Just as the pain of a heart attack comes
from insufficient blood to the muscles of the heart,
too little blood to the uterine muscle might cause
the pain of menstrual cramps.
Menstrual pain can have other causes, although these
are rare among teenagers. They include tumors,
fallopian tube infection, and endometriosis, a
condition in which fragments of the lining of the
uterus become embedded elsewhere in the body